Acting event manager Molly Devine said the alarm set the event back by 45 minutes, and some flights and hotel bookings had to be cancelled to accommodate the change.
Once the crowd returned to their seats, Miss Devine thanked everyone for their co-operation and said the firefighters were the real rock stars of the day.
The smoke machines were turned off for the afternoon.
"Smokefree Rockquest will be truly smoke-free," Miss Devine joked to the crowd.
She was glad everyone co-operated well throughout the evacuation, and that nobody complained.
She found it funny the crew had to drive only a few metres across the road.
Aside from the interruption, the event was fast-paced and lots of fun, Miss Devine said.
Thirty bands took part in the regional heat, each playing one song under five minutes long.
Twelve of those bands would be selected for the regional final on June 25, she said.
There was also an award for the best solo/duo act, and one for the best use of Maori and Pasifica elements in a performance, such as instruments, lyrics, or dance.
Local band The Velvet Strings had just left the stage when the alarm went off.
Bassist Seth Fleming (17) said he was glad the band got to finish its song, and the members were not really sure what was happening when they left the building.